I appreciate all your time and help, guys. Excuse me for not mentioning the cathode resistor for bias.
>From what little I have found...both the Collins 310A exciter and WRL Globe >King 275 use a 6SJ7 for mike input...in which case, a hi-Z dynamic should work. So...back to square #1 - what is "hi"? Mouser has cheap ( $4 ) crystal elements whose impedance range is from 9K to 25K which doesn't look "hi" to me. I've also read that a ceramic element - acting in the same fashion as the piezoelectric - can be used. Which means that my Electro-Voice 729 is a candidate which is already on my shelf...sparkling since I polished all that cast metal to high sheen. The modulators are 2 x 807's going into an RF deck of 2 X 1625's having link coupled input from a 6L6 oscillator or 6L6 doubler stages...fortunately, I can get the 3.5715 Mc FT 243 type rock from PR Crystal for my 20 meter AM freq 14.286...only $15. Working on this restoration is a great learning experience for me...and again, I sincerely appreciate you sharing with this rookie. Regards, Steve WA2TAK PS...the 813 homebrew restoration is in the workshop patiently waiting for me...another 1x3 - now SK - in North Carolina made it.
